Only the front wheel bearings require periodic maintenance. A premium high melting point grease meeting GM specification 6031-M must be used. Long fiber type greases must not be used. This service is recommended at the intervals in the Maintenance Intervals Chart or whenever the truck has been driven in water up to the hubs.
Before handling the bearings, there are a few things that you should remember to do and not to do.Remember to do the following:
Do not do the following:
REMOVAL, PACKING & INSTALLATION
Sodium-based grease is not compatible with lithium-based grease. Read the package labels and be careful not to mix the two types. If there is any doubt as to the type of grease used, completely clean the old grease from the bearing and hub before replacing.2-Wheel Drive
See Figures 1 through 18
- Raise and support the front end on jackstands.
- Remove the wheel.
- Dismount the caliper and wire it out of the way.
- Pry out the grease cap, remove the cotter pin, spindle nut, and washer, then remove the hub. Do not drop the wheel bearings.
- Remove the outer roller bearing assembly from the hub. The inner bearing assembly will remain in the hub and may be removed after prying out the inner seal. Discard the seal.
- Clean all parts in a non-flammable solvent and let them air dry. Never spin-dry a bearing with compressed air! Check for excessive wear and damage.
- Using a hammer and drift, remove the bearing races from the hub. They are driven out from the inside out. When installing new races, make sure that they are not cocked and that they are fully seated against the hub shoulder.
- Pack both wheel bearings using high melting point wheel bearing grease for disc brakes. Ordinary grease will melt and ooze out ruining the pads. Bearings should be packed using a cone-type wheel bearing greaser tool. If one is not available they may be packed by hand.
- Place a healthy glob of grease in the palm of one hand and force the edge of the bearing into it so that the grease fills the bearing. Do this until the whole bearing is packed.
- Place the inner bearing in the hub and install a new inner seal, making sure that the seal flange faces the bearing race.
- Carefully install the wheel hub over the spindle.
- Using your hands, firmly press the outer bearing into the hub. Install the spindle washer and nut.
- Spin the wheel hub by hand and tighten the nut until it is just snug; 12 ft. lbs. (16 Nm).
- Back off the nut until it is loose, then tighten it finger tight. Loosen the nut until either hole in the spindle lines up with a slot in the nut and insert a new cotter pin.
- There should be 0.001-0.005 in. (0.025-0.127mm) end-play on 1988-90 models. On 1991-98 models, end-play should be 0.005-0.008 in. (0.013-0.20mm) on HD models. This can be measured with a dial indicator, if you wish.
- Replace the dust cap, wheel and tire.
Before starting you'll need a special wheel bearing nut socket for your1/2inch drive ratchet. These sockets are available through auto parts stores and catalogs. You can't do this job properly without it! You'll also need a1/2inch drive torque wrench, a clean container, like a shoe box, for the parts as you remove them and PLENTY of paper towels handy.
- Raise and support the front end on jackstands.
- Remove the wheels.
- Remove the hubs. See the Section 7.
- Wipe the inside of the hub to remove as much grease as possible.
- Using your bearing nut socket, remove the locknut from the spindle.
- With the locknut off you'll be able to see the locking ring on the adjusting nut. Remove the locking ring. A tool such as a dental pick will make this easier.
- Using the special socket, remove the bearing adjusting nut.
You'll notice that the adjusting nut and the locknut are almost identical. The difference is, the adjusting nut has a small pin on one side which indexes with a hole in the locking ring. DO NOT CONFUSE THE TWO NUTS!
- Dismount the brake caliper and suspend it out of the way, without disconnecting the brake line. See Brakes .
- Pull the hub off of the spindle. The outer bearing will tend to fall out as soon as it clears the spindle, so have a hand ready to catch it.
- If you are going to reuse the outer bearing, place it on a clean surface.
- Position the hub, face up, on 2 wood blocks placed under opposite sides of the rotor. Have a paper towel positioned under the hub.
- Using a hardened wood dowel or a hammer handle, drive out the inner bearing and seal. If your are going to reuse the inner bearing, move it to a clean area. Discard the seal.
- If the bearings are being replaced, you'll have to replace the races. The races are pressed into the hub, but you can drive them out. With the hub in position on the blocks, use a long drift and hammer evenly around the outside diameter of the inner bearing race until it is free. Discard the race. Turn the hub over and repeat this procedure for the outer bearing race.
- wash the bearings in a non-flammable solvent and let them air-dry. Never use compressed air to spin-dry the bearings!
- If either bearing shows any sign of damage, rust, heat blueing or excessive looseness, both bearings in that hub must be replaced as a set. If bearings are replaced, the races MUST be replaced also!
If the bearings show signs of heat blueing, wipe the spindle clean and check for heat blueing on the spindle surface. If the spindle shows large areas of heat blueing, it should be replaced.
- Wash out the hub with solvent and wipe it clean. Check the races. If they show signs of wear, pitting, cracking, rusting or heat blueing, they, along with the bearings, must be replaced.
- Coat the race and its bore in the hub with high temperature wheel bearing grease.
- Position the race in the bore and start gently tapping it into place. There are drivers made for this purpose, but you can do it with a blunt drift and hammer. Just tap evenly around the race as you drive it into place so that it doesn't cock in the bore.
Drive the race in until it is fully seated against the shoulder in the bore. You can tell that it's fully seated in two ways:
- Your hammer blows will sound differently when the race seats against the shoulder.
- The grease you applied to the bore will be squeezed out below the race as the race seats against the shoulder.
Either race can be installed first.
Pack the bearings thoroughly with high temperature wheel bearing grease. An inexpensive wheel bearing packing tool is available at most auto parts stores. The tool has a grease fitting which utilizes a grease gun and completely packs the bearing. You can, however, pack a bearing reasonably well without the tool:
- Open the container of grease.
- Force the bearing down into the container, first on one side, then the other, until grease squeezes out among the rollers.
- Place a large blob of grease in the palm of one hand and force the bearing into the grease to squeeze out any air cavities among the rollers. When you're satisfied that each bearing is completely packed, place them on a clean paper towel, in a clean area, and cover them with another clean paper towel.
- Pack the area of the hub, between the races, with wheel bearing grease.
- Place the inner bearing in its race and position a new seal in the hub bore. Gently tap around the outer diameter of the seal with a plastic mallet until the seal is flush with the end of the bore.
- Carefully place the hub assembly on the spindle. Take care to avoid damaging the seal on the spindle threads. Make sure the hub is all the way on the spindle.
- Place the outer bearing on the spindle and slide it into place in its race.
- Thread the adjusting nut on the spindle until it contacts the outer bearing.
Using the special socket and the torque wrench:
- Tighten the adjusting nut to 50 ft. lbs. (67 Nm) while rotating the hub.
- Back off the adjusting nut until it is loose.
- While rotating the hub, tighten the adjusting nut to 35 ft. lbs. (48 Nm) for automatic locking hubs or 50 ft. lbs. (67 Nm) for manual locking hubs.
- Back off the adjusting nut 1 / 4 - 3 / 8 of a turn for automatic hubs or 1 / 6 - 1 / 4 of a turn for manual hubs.
- Coat the locking ring with wheel bearing grease. Place the locking ring on the spindle. There is a tab on the inner diameter of the ring which must fit in the slot on the top of the spindle. Slide the locking ring in until it contacts the adjusting nut. The pin on the adjusting nut must enter one of the holes in the locking ring. You can tell that the locking ring is seated properly when you see the grease on the ring get pushed out of one of the holes by the pin, and the ring does not rock from side-to-side when you press on either side with your finger. If the locking ring and pin don't index, take note of how far off they are, pull the ring off the spindle and turn the nut, either by hand or with the socket, just enough for a good fit. Try the locking ring again.
- When the locking ring engages the adjusting nut pin properly, your bearing adjustment is set. Thread the locknut onto the spindle until it contacts the locking ring.
- Tighten the locknut to at least 160 ft. lbs. (216 Nm). This locknut ensures that the locking ring and adjusting nut don't move. Over-tightening the locknut has no effect on the bearing adjustment.
- Install the locking hub.
- Install the caliper.
- Install the wheel.
These axles have integral hub/bearing assemblies. No periodic service is required. See Drive Train for disassembly details.